1. Field of the Invention
This invention pertains to insulated doors of the type used in refrigerated or controlled environment storage warehouses.
2. Description of the Prior Art
Warehouses for storing perishable commodities, such as apples, have long had the need for insulated doors to seal the interior of the warehouse from outside temperature, atmosphere or both. Some of these doors must be large enough to accommodate large forklift trucks carrying the commodity into or out of the warehouse.
The operator's visibility is poor with a loaded forklift truck. Furthermore, some of the large doors are automatically operated to open and close in the minimum amount of time to minimize the loss of the controlled temperature or gaseous environment within the warehouse. As a result, doors are frequently being hit by the loaded forklift carrier due to various circumstances, such as a door closing after the passage of a first loaded forklift into the path of an oncoming second loaded forklift.
Although the damage to the door generally occurs at the lower end of the door, heretofore the damage has required replacement of the entire door to maintain the tight insulating and atmosphere-sealing capability of the door critical to operation of the warehouse. Prior art doors are most commonly made of plywood and weigh approximately five to seven pounds per square foot; thus a ten foot by twelve foot door will frequently weigh as much as 720 pounds and require mechanized equipment plus a crew of at least three men to replace the door. This, of course, is expensive and requires long periods of delay in replacing the door due to the lack of the equipment or available workmen for replacement.